Dataset Information

Mechanism for inactivation of the mitotic inhibitory kinase Wee1 at M phase.

ABSTRACT: Wee1, the inhibitory kinase of cyclin B/Cdc2, undergoes a phosphorylation-dependent catalytic inactivation at M phase of the mitotic cell cycle, but the precise mechanism for this inactivation is not known. Using Xenopus egg and extract systems, we show here that the kinase activity of Xenopus somatic Wee1 (XeWee1B) is regulated by its N-terminal, small, well conserved region, termed here the Wee-box. The Wee-box is essential for the normal kinase activity of XeWee1B during interphase, acting positively on the C-terminal catalytic domain, which alone cannot efficiently phosphorylate Cdc2. Significantly, a Thr-186-Pro (TP) motif within the Wee-box is phosphorylated by Cdc2 at M phase and specifically binds the cis/trans prolyl isomerase Pin1. This Pin1 binding is required for the inactivation of XeWee1B at M phase, presumably causing isomerization of the phospho-TP motif and thereby impairing the function of the Wee-box. These results provide important insights into the mechanism of Wee1 inactivation at M phase.

SUBMITTER: Okamoto K

PROVIDER: S-EPMC1820656 | biostudies-literature | 2007 Mar

REPOSITORIES: biostudies-literature

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Mechanism for inactivation of the mitotic inhibitory kinase Wee1 at M phase.

Okamoto Kengo K Sagata Noriyuki N

Proceedings of the National Academy of Sciences of the United States of America 20070223 10

Wee1, the inhibitory kinase of cyclin B/Cdc2, undergoes a phosphorylation-dependent catalytic inactivation at M phase of the mitotic cell cycle, but the precise mechanism for this inactivation is not known. Using Xenopus egg and extract systems, we show here that the kinase activity of Xenopus somatic Wee1 (XeWee1B) is regulated by its N-terminal, small, well conserved region, termed here the Wee-box. The Wee-box is essential for the normal kinase activity of XeWee1B during interphase, acting po ...[more]

PMID: 17360425

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Project description:BackgroundThe inhibitory effect of andrographolide sodium bisulphite (ASB) on jack bean urease (JBU) and Helicobacter pylori urease (HPU) was performed to elucidate the inhibitory potency, kinetics and mechanism of inhibition in 20 mM phosphate buffer, pH 7.0, 2 mM EDTA, 25 °C.MethodsThe ammonia formations, indicator of urease activity, were examined using modified spectrophotometric Berthelot (phenol-hypochlorite) method. The inhibitory effect of ASB was characterized with IC50 values. Lineweaver-Burk and Dixon plots for JBU inhibition of ASB was constructed from the kinetic data. SH-blocking reagents and competitive active site Ni2+ binding inhibitors were employed for mechanism study. Molecular docking technique was used to provide some information on binding conformations as well as confirm the inhibition mode.ResultsThe IC50 of ASB against JBU and HPU was 3.28±0.13 mM and 3.17±0.34 mM, respectively. The inhibition proved to be competitive and concentration- dependent in a slow-binding progress. The rapid formation of initial ASB-JBU complex with an inhibition constant of Ki=2.86×10(-3) mM was followed by a slow isomerization into the final complex with an overall inhibition constant of Ki*=1.33×10(-4) mM. The protective experiment proved that the urease active site is involved in the binding of ASB. Thiol reagents (L-cysteine and dithiothreithol) strongly protect the enzyme from the loss of enzymatic activity, while boric acid and fluoride show weaker protection, indicating that the active-site sulfhydryl group of JBU was potentially involved in the blocking process. Moreover, inhibition of ASB proved to be reversible since ASB-inactivated JBU could be reactivated by dithiothreitol application. Molecular docking assay suggested that ASB made contacts with the important sulfhydryl group Cys-592 residue and restricted the mobility of the active-site flap.ConclusionsASB was a competitive inhibitor targeting thiol groups of urease in a slow-binding manner both reversibly and concentration-dependently, serving as a promising urease inhibitor for the treatment of urease-related diseases.

Dataset Information

Mechanism for inactivation of the mitotic inhibitory kinase Wee1 at M phase.

Publications

Mechanism for inactivation of the mitotic inhibitory kinase Wee1 at M phase.

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